The calendar got one wrong. How do I undo it?

On the From your calendar page of the evening check-in, every saved event has two buttons, and they do different things.

1. Undo removes the log entry that was saved. That is all. A future event with the same title can still be suggested again.
2. Never suggest again removes the log entry and remembers that you opted out of this title. The next time an event with that name appears, it is skipped instead of saved.

For a one-off mistake, tap Undo. For something you never want logged, like "Dentist", tap Never suggest again.

What if I change my mind?

1. Tap the gear icon in the top-left and tap Manage Items.
2. Open Calendar opt-outs ("Titles you've undone from calendar").
3. Each title you opted out of is listed with how many events it covered. Tap the bin next to a title to forget that opt-out.

The next time a matching event shows up in your calendar, it is classified fresh and may be saved again.

Will the same event be logged twice?

No. VertigoMe remembers each calendar event, so as a planned event moves closer (6 days away, then 5, then 4) it is not added again. Your earlier decision on that event stays.